In this image, the dark pink areas show land masses where two or three satellites recorded surface melting this month. Light pink, or “probable melt” areas, were identified by one satellite as having surface melting.

Heavy melting during mid-July covered a larger area than at any time in more than 30 years, NASA reported.

The melting far exceeded Greenland’s average summer melting, which affects about half of the surface of Greenland’s ice sheet.

It remains unclear how this surface melting will affect the overall volume of ice loss.

One researcher said the melting was so extraordinary, he questioned the results at first; but a doublecheck found that the satellite readings he was seeing at the Indian Space Research Organization’s (ISRO) Oceansat-2 satellite tracked with information from NASA’s Terra and Aqua satellites.

The extreme melting coincided with a strong blast of warm air, known as a heat dome, that settled over Greenland, just one of the many factors that affects weather in that frozen land.

“The Greenland ice sheet is a vast area with a varied history of change. This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story,” said Tom Wagner, NASA’s cryosphere program manager in Washington. “Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system.”

Ice cores taken from central Greenland show that melting events do occur about once every 150 years, according to researcher Lora Koenig at NASA’s Goddard Space Flight Center in Maryland.

“But if we continue to observe melting events like this in upcoming years,” she said, “it will be worrisome.”